This study reports the eco-friendly synthesis of zinc oxide nanoparticles (ZnO NPs) using Pisum sativum seed extract as a natural reducing and stabilizing agent. The biosynthesized ZnO NPs were characterized by UV-vis spectroscopy, XRD, FTIR, and FE-SEM, revealing predominantly spherical nanoparticles with uniform distribution, sizes of 30–50 nm, and aggregation driven by polarity and electrostatic interactions. Their adsorption performance was evaluated for the removal of Congo Red (CR) dye from aqueous solutions. Batch experiments demonstrated a maximum removal efficiency of ∼91% under optimal conditions (14 mg L−1 dye concentration, pH 6, 35 °C, 0.015 g adsorbent dose, and 40 min contact time). Adsorption followed pseudo-second-order kinetics, indicating chemisorption, and fit both Langmuir and Freundlich isotherm models, suggesting a combination of monolayer and multilayer adsorption on a heterogeneous surface. Thermodynamic analysis confirmed the process to be spontaneous, endothermic, and associated with decreased randomness at the solid–solution interface, with enhanced efficiency at higher temperatures. These results highlight the potential of Pisum sativummediated ZnO NPs as an efficient and promising eco-friendly adsorbent for wastewater treatment and dye removal. Further studies on desorption and regeneration cycles are required to evaluate long-term adsorbent sustainability.

A new, quick, economical, accurate and precise spectrophotometric method was developed for the determination of sulfanilamide in its pure form. This technique focused on the reaction of this amine as an n-donor via the charge-transfer complex formation reaction with pyromellitic dianhydride (PMDA) as a p-acceptor. The maximum absorption of sulfanilamide was at 258 nm. Beer's law was observed over the concentration range of 0.2–35 mg mL−1 with a molar absorptivity value of 16 226.24 L mol−1 cm−1 . The accuracy of the method (average recovery %) was 101.501%, and its precision (RSD %) was less than 0.6%. The nature of PMDA complexes with sulfanilamide was studied using the mole ratio method. The findings demonstrated that this complex was produced in a ratio of 1 : 1 with a stability constant of 2.49 × 108 L mol−1 for the amine-PMDA complex. The detection limit (LOD) was 0.0136 mg mL−1 , and the limit of quantification (LOQ) was 0.0412 mg mL−1 . DFT calculations were employed to learn more about the charge transfer mechanism. Density of states (DOS) calculations demonstrated electronic interactions near the Fermi level, in which nitrogen and sulfur orbitals from sulfanilamide act as electron donors, while the carbonyl group and aromatic system of PMDA act as electron acceptors. HOMO– LUMO analysis further confirmed this donor–acceptor mechanism.

A novel, easy, quick and precise spectrophotometric technique has been established for the evaluation of catecholamines (methyldopa, levodopa, dopamine and carbidopa) in pure forms and in their pharmaceutical preparations, this technique is focused on the reaction of these catecholamines as n donor with pyromellitic dianhydride as π acceptor in the presence of sodium hydroxide. The maximum absorptions at 300, 302, 301, and 298 nm for methyldopa, levodopa, dopamine and carbidopa respectively. In a concentration range of Beer's law was obeyed 0.2-40, 0.2-40, 0.2-50 and 0.2-100 µg.mL-1 with molar absorptivities 9921.2975, 8982.8334, 6430.8797 and 5022.7469 L/mol.cm for the catecholamines respectively. The accuracy range between 98.843% and 100.891% and RSD% is less than 2% for the above catecholamines respectively. The detection limit (LOD) was 0.0518, 0.0581, 0.0638 and 0.0579 µg.mL-1 and limit of quantification (LOQ) was 0.1571, 0.1762, 0.1935 and 0.1756 µg.mL-1 for the above catecholamines in turn. The suggested method was successfully used to the analysis of catecholamines in pure as well as medications formulation with a good average recovery.